GBU-12 Viper vs. Hornet

[Bricux]

The topic is, after the last bomb update (now they can pierce ceilings after setting the fuse) I wanted to try it out in the Hornet trial. I noticed that the Hornet GBU-12 can be set to delay the fuse, while the Viper not (only NSTL-NOSE-TAIL). To my knowledge, they should both be identical bombs. Meanwhile, in Hornet in the newer GBU-24 bomb, only (NSTL-NOSE-TAIL) can be set.

Could someone check / explain it? Thanks!

[Northstar98]

1 hour ago, Bricux said:

The topic is, after the last bomb update (now they can pierce ceilings after setting the fuse) I wanted to try it out in the Hornet trial. I noticed that the Hornet GBU-12 can be set to delay the fuse, while the Viper not (only NSTL-NOSE-TAIL). To my knowledge, they should both be identical bombs. Meanwhile, in Hornet in the newer GBU-24 bomb, only (NSTL-NOSE-TAIL) can be set.

Could someone check / explain it? Thanks!

AFAIK GBU-12s have an electric tail fuse (FMU-139), which can detonate on impact or after a short delay (according to this, they can also be used with a proximity sensor, but the CCG obviously precludes that).

According to Scrape, the nose fuse setting activates the CCG (which is the control group on the front, including the seeker and control surfaces), and the tail fusing option activates the fuse, so they should be dropped in N/T.

No idea how the F-16CM handles fuse settings, maybe they have to be preprogrammed on the bomb beforehand?

Edited October 16, 2021 by Northstar98

[Frederf]

For all USAF or USN/USMC mechanical operations the FMU-139 itself is initiated by the tail arming option. The FZU-48 which powers the fuze is imitated by the center arming latch (always). A Paveway II is typically configured such that the nose option selects initiation of the CCG arming for guidance. The selections N, T, N/T result in guided dud, unguided detonation, and guided detonation respectively.

For USN/USMC FFCS operations the FMU-139 may or may not have a mechanical arming wire. Electrical power and signal is supplied through the MK 112 safety switch through a cable installed in place of FZU-48 as described above. The CCG requires an arming lanyard as described above. When no lanyard safety on the FMU-139 is present the FFCS charge determines if the fuze is powered or not.

In the mechanical operation case the arming time and functioning delay are determined by the arming wires, deceleration sense, and faceplate settings on the fuze. The low drag settings are X 4 6 7 10 14 20 and control when the bomb becomes armed if no deceleration is sensed, X corresponding to electronic control which will never arm with mechanical operation. The low drag settings are 2 4 5 2.6 which determine what the arming time is when deceleration is sensed (high drag). The high drag settings also determine the functioning delay for all modes INST 10 25 60 milliseconds. For example a low drag bomb with low drag setting 7 and high drag setting 4.0/25 or 2.6/25 would arm after 7 seconds and have a 25ms functioning delay.

The pilot may only arm or not arm the bomb while flying but that is the only control available. It will arm and function according to the faceplate.

In electronic operation the low drag setting may be set to X which gives the FFCS the ability to set 5.5 or 10s arming time in flight. The high drag setting determines the functioning delay if the FFCS sends the DLY1 or VT signal during release. If the FFCS sends the instant signal then the detonation is instantaneous regardless of faceplate setting. If the faceplate setting is 2.6/INST for example then there is no difference between INST and DLY1 as set in flight.

The pilot may arm or not arm the bomb, set 5.5 or 10s AD, and choose whether to use the function delay as set or override it to instantaneous in flight.

---

In order to get delayed function with the F-16 it is necessary that the high drag/delay setting be made on the faceplate before flight. This is also true of the F-18. The F-18 only has the additional ability to override the faceplate setting for instant function.

 

[Bricux]

13 minutes ago, Frederf said:

For all USAF or USN/USMC mechanical operations the FMU-139 itself is initiated by the tail arming option. The FZU-48 which powers the fuze is imitated by the center arming latch (always). A Paveway II is typically configured such that the nose option selects initiation of the CCG arming for guidance. The selections N, T, N/T result in guided dud, unguided detonation, and guided detonation respectively.

For USN/USMC FFCS operations the FMU-139 may or may not have a mechanical arming wire. Electrical power and signal is supplied through the MK 112 safety switch through a cable installed in place of FZU-48 as described above. The CCG requires an arming lanyard as described above. When no lanyard safety on the FMU-139 is present the FFCS charge determines if the fuze is powered or not.

In the mechanical operation case the arming time and functioning delay are determined by the arming wires, deceleration sense, and faceplate settings on the fuze. The low drag settings are X 4 6 7 10 14 20 and control when the bomb becomes armed if no deceleration is sensed, X corresponding to electronic control which will never arm with mechanical operation. The low drag settings are 2 4 5 2.6 which determine what the arming time is when deceleration is sensed (high drag). The high drag settings also determine the functioning delay for all modes INST 10 25 60 milliseconds. For example a low drag bomb with low drag setting 7 and high drag setting 4.0/25 or 2.6/25 would arm after 7 seconds and have a 25ms functioning delay.

The pilot may only arm or not arm the bomb while flying but that is the only control available. It will arm and function according to the faceplate.

In electronic operation the low drag setting may be set to X which gives the FFCS the ability to set 5.5 or 10s arming time in flight. The high drag setting determines the functioning delay if the FFCS sends the DLY1 or VT signal during release. If the FFCS sends the instant signal then the detonation is instantaneous regardless of faceplate setting. If the faceplate setting is 2.6/INST for example then there is no difference between INST and DLY1 as set in flight.

The pilot may arm or not arm the bomb, set 5.5 or 10s AD, and choose whether to use the function delay as set or override it to instantaneous in flight.

---

In order to get delayed function with the F-16 it is necessary that the high drag/delay setting be made on the faceplate before flight. This is also true of the F-18. The F-18 only has the additional ability to override the faceplate setting for instant function.

 

So I guess it should be function similar like setting laser code by kneeboard on the ground?

[Frederf]

Bomb fuzes are not super detailed in DCS or at least not to the point the user can adjust it. My guess is that behavior is hard coded F-18 is instant/delay F-16 always instant. Since there's no control then forcing delay function all the time would lead to more complaints.

[Bagpipe]

https://www.kaman.com/sites/default/files/FMU-152AB-DataSheet2017-pages-PRINT.pdf

 

I am gonna guess firstly that it is a new feature to that particular weapon which has yet to be implemented to the viper module. So not a bug just an incomplete feature.

Second guess would be that, as per the attached document, it might depend on whether the F-16 uses the necessary stores interconnect system to actually change the fuze delay setting "on the fly" or not. It may be that the hornet can and with the viper the ground crew have to manually prepare them. I can't find any documents telling me either way, maybe ED can't? More likely the first guess though in honesty  If it is down to the ground crew then, of course, ED will have to code that in to the comms menu when the payload contains this bomb so either way it is not a straight argument of "the hornet has it so the viper should" in my humble opinion. 

Edited October 16, 2021 by Bagpipe

[Falconeer]

17 hours ago, Northstar98 said:

AFAIK GBU-12s have an electric tail fuse (FMU-139), which can detonate on impact or after a short delay (according to this, they can also be used with a proximity sensor, but the CCG obviously precludes that).

According to Scrape, the nose fuse setting activates the CCG (which is the control group on the front, including the seeker and control surfaces), and the tail fusing option activates the fuse, so they should be dropped in N/T.

No idea how the F-16CM handles fuse settings, maybe they have to be preprogrammed on the bomb beforehand?

 

 

- CCG is the head of the bomb and its only there to guide it to the target. It does nothing with the fuses and it gets activated by an internal battery, as soon as the bomb is released. 

- ECCG (GBU-49 for example) has a proximity fuse or HOB sensor

- The nose fuse (if installed) is armed with a second arming solenoide which is in the center of the bomb rack. The nose and center arming solenoides are tied to each other. Tail is a seperate arming  solenoide. 

- LGB's can also be equiped with a mechanical fuse in the tail, which would be the M905 fuse together with an ATU35

- And lastly, the fuses are set on the ground, for the nose, we need to remove the CCG. For the tail, there is a small acces door

 

Edited October 17, 2021 by Falconeer

[Falconeer]

57 minutes ago, Bricux said:

So I guess it should be function similar like setting laser code by kneeboard on the ground?

That depends on which fuse is used.  

Some can only be set on the ground like the FMU-139B/B, while a FMU-152A/B can be programmed from the cockpit

 

Edited October 16, 2021 by Falconeer

[Bagpipe]

An idea would be for the loadout UI menu to include the sorts of options available to the ground crew, or at least the important ones. I would love to see that, others may not enjoy it though

[Northstar98]

15 hours ago, Bagpipe said:

An idea would be for the loadout UI menu to include the sorts of options available to the ground crew, or at least the important ones. I would love to see that, others may not enjoy it though

Maybe in the loadout and rearming UIs for the mission editor and ground crew, at the moment right clicking on a pylon brings up a list of weapons.

Once a weapon is selected, we could left click on it and that would bring up a menu that allows us to change different parameters of the selected weapon, where applicable; things like fuses and fuse settings (at least for pre-set fuses), nose caps (for things like JDAMs), laser codes for the Paveway II and III(?) series and APKWS etc.

Edited October 17, 2021 by Northstar98

[Bagpipe]

1 hour ago, Northstar98 said:

Maybe in the loadout and rearming UIs for the mission editor, at the moment right clicking on a pylon brings up a list of weapons.

Once a weapon is selected, we could left click on it and that would bring up a menu that allows us to change different parameters of the selected weapon, where applicable; things like fuses and fuse settings (at least for pre-set fuses), nose caps (for things like JDAMs), laser codes for the Paveway II and III(?) series and APKWS etc.

Precisely what I meant but better worded  Even better, If when we left click on it a small window popped out with a small "encyclopedia" page with detailed info, IRL image(s) and the options. Ahhh

Edited October 17, 2021 by Bagpipe